Long-Term Outcomes in Patients With Isocitrate Dehydrogenase–Mutated Grade 2 Glioma Who Never Received Adjuvant Oncological Treatment After Upfront Mapping–Based Surgical Resection

BACKGROUND AND OBJECTIVES: Patients with low-grade glioma (LGG) have a long-life expectancy, especially after initial surgery. However, no report specifically investigated LGG patients who underwent only resection without oncological therapy. In this study, long-run outcomes were analyzed in LGG patients who never received adjuvant treatment after upfront mapping–based surgical resection. METHODS: Inclusion criteria were patients operated on by the author using intraoperative mapping for isocitrate dehydrogenase–mutated grade 2 gliomas, followed at least 3 years with no oncological treatment at last evaluation. Two groups were compared: group 1 comprising stable LGG or progressing very slowly (growth rate ≤1 mm/year) with a simple monitoring and group 2 comprising recurrent LGG (growth rate >1 mm/year), including patients who underwent reoperation(s). RESULTS: This consecutive series included 111 patients (49 men, mean age 37.3 ± 10.4 years) with epilepsy in 74 cases (66.7%). The mean Karnofsky Performance Scale (KPS) score was 96.5 ± 5.7; 98 patients (88.3%) worked before surgery. The mean preoperative tumor volume (TV) was 21.4 ± 17.2 cm 3 . The mean postoperative KPS score was 96.7 ± 5.3 (no permanent deficit) with 92 patients who returned to work (93.8%). The mean extent of resection was 98.1 ± 4.7%, with 85 supratotal/total resections (76.6%)—mean residual TV of 0.6 ± 1.6 cm 3 . There were 60 isocitrate dehydrogenase–mutant astrocytomas (54%) and 51 oligodendrogliomas. Forty-nine patients (44.1%) underwent reoperation(s) without deterioration after 164 resections. The mean follow-up was 8.3 ± 4 years with an overall survival rate of 100%. At final evaluation, 108 patients (97.3%) had a KPS score ≥80 and 79 patients (80.6%) continued to work. In group 1, patients were older ( P = .0009) with lower preoperative TV ( P = .028), greater extent of resection ( P = .002), higher rate of (supra)total resections ( P = .024), and lower postoperative TV ( P = .0009). The growth rate was higher in patients with reoperation ( P < .0001). CONCLUSION: Postoperative simple monitoring can be considered in selected patients after upfront mapping–based surgery for LGG, especially when (supra)marginal resection was achieved in tumor with slow growth rate, even after the age of 40 years.